My 129 powered down while mowing...not sure why?
 

Granted that I mowed really heavy stuff for close to 2 hours, and it's another pretty hot day. But still, can't recall this ever happening before. It simply throttled down and stopped. Then, couldn't get it started for about 5 minutes. Cranked ok but that's it. Finally started, but it was kind of limping along. Seemed worse with increased throttle so I kept at low speed. Luckily I was close to my house at that point. Governor seemed quite erratic though. Got it inside the garage, cleaned everything up from mowing. All looks ok underneath, and oil level's full. Tried again about 15 minutes later and it starts right up and sounds fine.

Are these old machines thermally protected somehow and so shut off when overheated? I'm thinking probably not but thought I'd ask. So then I guess I'm looking at possible carburetor issues.

New engine went in back in '15 and lots of other items replaced at the same time. Doesn't really get used that hard - maybe once every few weeks for 1 1/2 - 2 hours each time, but this time especially I had to mow through really heavy weeds.

See what happens next time I suppose but thanks for any suggestions in the meantime. Some quick research in older threads show others mentioning overheating with the suggestion that the coil might be going bad. Coil and all electrical components were new as of '15 with the engine replacement. Plug, air and fuel filters get replaced every spring. Grass screen gets cleaned before every mowing, as does the front grille (after each mowing) to make sure all those holes are open. I also clean around the entire bottom area - removing obvious dirt, etc. around the trans and filter. Hydraulic oil is routinely checked as well. Should have added that it was running great all the way up until when it stopped.

Just off the top of my head, my first thought is that it sounds like a fuel problem. Dirt in the tank blocking the fuel flow to the bowl; blockage in the fuel line to the carburetor; maybe even something in the needle valve.

Make sure the vent in your gas cap is clear.

It does seem very likely to have been a temporary fuel delivery issue. It really reminded me of hitting a kill switch the way it powered down so quickly, which immediately led me to wonder about overheating.

I would not have thought of the vent in the gas cap though! With the dry weather, there was alot of dust and debris blowing around. I'll check out the cap, and otherwise if it happens again I'll have to do some carb work.

Thanks for the helpful replies!

In my limited experience, fuel delivery problems are usually not a instant dead stop problem but one where the engine starts to starve,then changes pitch, runs hot, sputters, then dies .



If it does it again, shoot some fuel directly in the carb and see if it instantly starts back up again...that should indicate a fuel issue.

If not, you're left with spark....

Keep posting! We love a mystery.

I had a similar situation with my my 149 last year, very hot day and beating it hard.
Started to run erratic amd then died. Cranked but no start.
It happened to be that the last time I replaced the fuel line I used clear see thru line.
When this situation occurred I could see the fuel in the line going into carb was bubbling and dancing around so I assumed it was boiling in the carb bowl.
After the activity died down in the fuel line it started and ran fine.
I guess they refer to this as fuel percolation, on older vehicles with carburetors you will hear mentiions of vapor lock.

Thanks for mentioning this. Seems so likely that I maybe experienced something very similar. I have regular black fuel line but it was really hot and I worked it hard, so it may well have been bubbling in there! No erratic running though before it died. It might remain a mystery. Find out next time perhaps.

Didn't really do that. It was more like I suddenly turned the key off. Motored down immediately. Thought maybe too much stuff caught under the deck, but that typically results in the belt squealing until I raise it a notch.

Besides fuel issues, you could have too much heat.
Check behind the tins between the fins. Then sometimes you can blow a head gasket.

So, again, we're talking about basically a potential overheating situation (?) Well, I doubt that it blew the gasket given that it started up and seems to be running ok. I suppose a compression test would determine it. Never did anything like that.